Rights object acquisition method of mobile terminal in digital right management system

ABSTRACT

A rights objects acquisition method of a mobile terminal in a digital right management system is provided for acquiring multiple rights objects in a composite manner. An objects right acquisition method of a mobile terminal may include generating, in response to a group rights object (RO) acquisition command, a group rights object acquisition request with content identifiers assigned to individual contents corresponding to the rights objects indicated by the group rights object acquisition command, sending the group rights object acquisition request to a rights issuer; and receiving an group rights object acquisition response containing rights object identifiers assigned to the rights objects from the rights issuer. The present invention streamlines the RO acquisition process, especially when acquiring multiple ROs.

CLAIM OF PRIORITY

The present application is a Continuation of U.S. patent applicationSer. No. 12/014,148 filed on Jan. 15, 2008 which in turn claims thebenefit of priority under 35 U.S.C. §119(a) from the following KoreanPatent Applications filed in the Korean Intellectual Property Office:(1) Serial No. 2007-0004166 filed on Jan. 15, 2007; (2) Serial no.2007-0046076 filed on May 11, 2007; and (3) Serial no. 2007-0056394filed on Jun. 9, 2007, the entire contents of each aforementioneddisclosure are hereby incorporated by reference in their entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a digital right management (DRM)system. More particularly, the present invention relates to a rightsobjects acquisition method of a mobile terminal in a digital rightmanagement system that is capable of delivering multiple rights objectsto a mobile terminal simultaneously.

2. Description of the Related Art

With the recent tendency toward digital convergence, mobile terminalsare evolving into multifunctional devices. For example, thefunctionality of mobile terminals now may include capabilities such asMP3 players and digital broadcast players by incorporating MP3 anddigital broadcast tuner modules. Such multimedia-enabled mobileterminals may also support various multimedia services, such as wirelessInternet access, online games, Music On Demand (MOD), and Video OnDemand (VOD). The ongoing diversification of the mobile services and theterminal capabilities continue to expand the utilizations of mobileterminals. The mobile content business has also expanded to includeenabling the provision of various types of mobile contents includingringtones, motion pictures, music files, and games, many of which arevaluable copyrighted materials. Since these mobile contents aretypically delivered to end users as pay contents, there is a need toprotect the contents from theft and prying eyes.

Digital Rights Management (DRM) now plays an ever-increasing role toprotect the pay contents from mobile terminal service providers and usedin mobile terminals from piracy and illegal copying. DRM is specificallyprovides a controlled consumption of digital contents, such asdocuments, audio files including voice and music files and ring tones,video files, and games to protect the intellectual property right of theauthors and the content providers.

Although DRM content object can be freely downloaded, it is useless to auser without a usage right, because without the corresponding RightsObject (RO), the material cannot be accessed since the DRM contentobjects are encrypted with a specific license key.

The RO is a container used in the Open Mobile Alliance (OMA) DRM system,which is an open DRM standard invented by the Open Mobile Alliance, forcarrying the license key to decrypt the corresponding DRM object. The ROis issued by a Right Issuer (RI) and purchased by the end user. Sincethe digital content and corresponding RO are delivered in a detachedmanner (typically separately), the usage of the downloaded content isrestricted to the user acquiring the corresponding RO. The RO is acollection of Permission, Constraints, and other attributes that defineunder what circumstances access is granted to a particular user, andwhat usages are defined for, DRM content object. Typically, the usageconstraints include Count, DateTime, Interval, Timed-Count, Accumulated,and Individual. The constraints are stored in a specific field of theRO.

For example, the RO may specify the usage for an MP3 file with the countconstraint value set to “10”. In this case, the MP3 file can be played10 times and the count is decremented by 1 each time the MP3 file isplayed. If the count reaches “0”, the usage right on the MP3 file isexhausted. In order to maintain the usage right on the MP3 file, thecorresponding RO should be updated.

FIGS. 1 a and 1 b are diagrams illustrating RO delivery procedures inconventional OMA DRM systems.

In FIGS. 1 a and 1 b, a mobile terminal 101 transmits a content requestmessage (105) to content server 102, and the content server 102transmits a corresponding content in response to the content requestmessage 106. In a case where the requested content is a DRM protectedcontent, the content is encrypted with an encryption key and with ascheme specified by the DRM, and transmitted in a DRM format having theconstraints (e.g., usage rule, the number of times to be played, andduration). If a user request for acquiring the license for thedownloaded content is detected, the mobile terminal 101 transmits alicense request message 107 to a Right Issuer (RI) 103, and the RI 103transmits the corresponding license 108 to the mobile terminal 101 inresponse to the license request message. Here, the license is a usageright on the content which includes a decryption key and usageconstraint information. In the case of a DRM content object, the mobileterminal 101 should acquire the usage right for consuming the content.Accordingly, the RI 103 checks whether the identity of the user of themobile terminal 101 is valid. If it is determined that the user isvalid, the RI 103 transmits the license to the mobile terminal 101. Ifthe license is received from the RI 103, the mobile terminal 101 iscapable of playing/accessing the content by using the license.Typically, the decryption key and usage constraint information areextracted from the license by a DRM client application installed in themobile terminal 101. The content is decrypted by using the decryptionkey and played under the usage constraints specified in the license.

FIG. 1 a shows an OMA DRM version 1.0 system in which the DRM ROcontaining a non-encrypted content encryption key (CEK) is deliveredfrom the RI server 103 to the mobile terminal 101. In the OMA DRMversion 1.0 system, there are serious shortcomings in that the contentcan be acquired and distributed by an unauthorized user who obtained theDRM Content Format (DCF) and RO (i.e., the license of the correspondingDRM content), simultaneously.

FIG. 1 b shows an OMA DRM version 2.0 system in which an authenticationauthority 104 (for example, Content Management Licensing Administrator:CMLA) is introduced. The CMLA 104 transfers the content encryption keysCEK 109 and 110, which are encrypted with a public key, to the mobileterminal 101 and the RI 103, respectively, and the RI 103 transfers theRO contained the encrypted CEK to the mobile terminal 101. Accordingly,in the OMA DRM version 2.0 system, the content can be decrypted only inthe mobile terminal 101 having the CEK, resulting in reinforcement ofusage right protection.

In the conventional OMA DRM version 2.0 system, however, each content isindividually protected by one RO, whereby the RO acquisition process,especially when acquiring multiple ROs, is laborious and time-consuming.For example, extending the validity of a number of ROs for expired MP3,video, and game files requires multiple RO purchasing processes,resulting a great degree of user inconvenience. Thus, there is a need inthe art for a more user convenient method that provides effectiveprotection of content.

SUMMARY OF THE INVENTION

The present invention has been made in part to solve at least some ofthe above problems and to provide at least some of the advantagesdiscussed herein below. The present invention provides an RO acquisitionmethod and apparatus that is capable of acquiring multiple ROs in acomposite manner.

Also, the present invention also provides an RO acquisition method andapparatus that is capable of increasing benefits both to consumers andDRM content providers, as well as improving user convenience bysimplifying the RO acquisition process.

Also, the present invention provides an RO acquisition method andapparatus that is capable of improving the efficiency of a DRM system bysimplifying the RO acquisition process in a composite manner.

In accordance with an exemplary aspect of the present invention, therights object acquisition method of mobile terminal includes generating,in response to a group rights object acquisition command, a group rightsobject acquisition request with content identifiers assigned toindividual contents corresponding to the rights objects indicated by thegroup rights object acquisition command; sending the group rights objectacquisition request to a rights issuer; and receiving a group rightsobject acquisition response containing rights object identifiersassigned to the rights objects from the rights issuer.

In accordance with another exemplary aspect of the present invention, arights object acquisition method of a mobile terminal includestransmitting a rights object acquisition protocol (ROAP) trigger requestreferencing multiple contents to a rights issuer; receiving an ROAPtrigger from the rights issuer in response to the ROAP trigger request;transmitting a rights object (RO) request referencing at least onecontent to the rights issuer after receiving the ROAP trigger; receivingan RO response from the rights issuer in response to the RO request; andacquiring at least one RO corresponding to the at least one content fromthe RO response.

In accordance with yet another exemplary aspect of the presentinvention, a rights object acquisition method in a digital rightsmanagement system includes transmitting, in response to a multiplerights object (RO) acquisition command, rights object acquisition (ROAP)trigger request referencing content identifiers (CIDs) assigned tomultiple DRM contents to a rights issuer (RI); receiving an ROAP triggerreferencing RO identifiers (roIDs) assigned to the ROs corresponding theDRM contents from the RI in response to the ROAP trigger request;transmitting an RO request referencing at least one DRM content selectedby a user to the RI after receiving the ROAP trigger; receiving an ROresponse containing at least one RO corresponding to the at least oneDRM content from the RI; and acquiring the at least one RO for the atleast one DRM content from the RO response.

In accordance with still another exemplary aspect of the presentinvention, a rights object acquisition method of a mobile terminal in adigital rights management (DRM) system includes generating, in responseto a group rights object acquisition command, a rights objectacquisition protocol (ROAP) trigger request; checking a common header ofa DRM content format (DCF) containing at least one DRM content;selecting a right issuer (RI) for acquiring rights objects (ROs)corresponding to at least one DRM content with reference to the commonheader; and transmitting the ROAP trigger request to the IR.

In accordance with still another exemplary aspect of the presentinvention, a rights object acquisition method for a digital rightsmanagement (DRM) system including a rights issuer (RI) issuing rightsobjects (ROs) to a mobile terminal includes receiving, at the RI, arights object acquisition protocol (ROAP) trigger request referencing aplurality of content identifiers (CIDs) assigned to a plurality ofcontents from the mobile terminal; generating ROAP trigger referencing aplurality of rights object identifiers (roIDs) assigned to the ROscorresponding to the contents; and transmitting the ROAP trigger to themobile terminal.

In accordance with another exemplary aspect of the present invention, arights object acquisition method of a mobile terminal includesgenerating, in response to a group rights object acquisition command, arights object acquisition protocol (ROAP) trigger request referencing aplurality of contents identifiers (CIDs) assigned to a plurality ofcontents indicated by the group rights object acquisition command;transmitting the ROAP trigger request to a rights issuer (RI) located bycommon uniform resource locator (BatchRIURL) headers of the contents;receiving an ROAP trigger referencing a plurality of rights objectidentifiers (roIDs) assigned to rights objects corresponding to thecontents from the RI; and acquiring at least one RO corresponding to atleast one content with reference to the roIDs in a composite manner

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionin conjunction with the accompanying drawings, in which:

FIG. 1 a and FIG. 1 b are diagrams illustrating RO delivery proceduresin conventional OMA DRM systems;

FIG. 2 is a block diagram illustrating an exemplary configuration of amobile terminal according to an exemplary embodiment of the presentinvention;

FIG. 3 a is a flowchart illustrating an overview of a rights objectacquisition method according to an exemplary embodiment of the presentinvention;

FIG. 3 b is diagram illustrating an exemplary data structure of an ROAPtrigger (RO response) message according to an exemplary embodiment ofthe present invention;

FIG. 4 is a message flow diagram illustrating an example of a rightsobject acquisition method according to an exemplary embodiment of thepresent invention;

FIG. 5 is a flowchart illustrating an example of a DRM content objectlist generation procedure of the rights object acquisition method ofFIG. 3 a;

FIG. 6 is a message flow diagram illustrating exemplary message flowsbetween entities in the DRM content list generation procedure of FIG. 5;

FIG. 7 is a flowchart illustrating examples of a DRM content listgeneration procedure of the rights object acquisition method of FIG. 3 aaccording to another exemplary embodiment of the present invention;

FIG. 8 is a message flow diagram illustrating exemplary message flowsbetween entities in the DRM content list generation procedure of FIG. 7;

FIG. 9 is a message flow diagram illustrating an exemplary rights objectacquisition method according to another exemplary embodiment of thepresent invention;

FIG. 10 is a message flow diagram illustrating a right objectacquisition method according to another exemplary embodiment of thepresent invention;

FIG. 11 a is an example of a screen image illustrating a step ofdisplaying the DRM content list in FIG. 4;

FIG. 11 b is a diagram illustrating an exemplary information fieldstructure of a DRM content list of FIG. 11 a;

FIG. 12 is a message flow diagram illustrating an exemplary rightsobject acquisition method according to another exemplary embodiment ofthe present invention;

FIG. 13 is a diagram illustrating a structure of DCF proposed for therights object acquisition method according to an exemplary embodiment ofthe present invention; and

FIG. 14 is a message flow diagram illustrating an exemplary rightsobject acquisition method according to another exemplary embodiment ofthe present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. It is to be understoodthat the drawings and examples discussed herein have been provided forillustrative purposes only, and the present invention is not limited tothe illustrative examples provided herein. The same reference numbersare used throughout the drawings to refer to the same or like parts. Forthe purposes of clarity and simplicity, detailed descriptions ofwell-known functions and structures incorporated herein may be omittedto avoid obscuring appreciation of the subject matter of the presentinvention by a person of ordinary skill in the art.

Table 1 comprises a list of abbreviations used in the followingexemplary detailed descriptions of the present invention.

TABLE 1 OMA Open Mobile Alliance DRM Digital Right Management DCF DRMContent Format RO Right Object (=License) ROAP Right Object AcquisitionProtocol FL Forward Lock CD Combined Delivery SD Separate Delivery CEKContent Encryption Key RI Right Issuer CI Content Issuer (=ContentServer) CA Certificate Authority OCSP Online Certificate Status ProtocolCMLA Content Management License Administrator

FIG. 2 is a block diagram illustrating a configuration of a mobileterminal according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the mobile terminal 200 includes a control unit201, an audio processing unit 204, an input unit 205, a radio frequency(RF) unit 206, a data processing unit 207, a memory unit 208, a cameraunit 209, a video processing unit 210, and a display unit 211.

The control unit 201 controls general operations of the mobile terminal200 and cooperative signaling between the internal elements of themobile terminal 200. In other words, the control unit 201 controls thecooperative signaling among the audio processing unit 204, input unit205, data processing unit 207, memory unit 208, camera unit 209, videoprocessing unit 210, and display unit 211.

If a play command is detected, the control unit 201 checks informationon the target DRM content file (e.g., DCF file) and performs a series ofprocesses for decoding and playing the DRM content file.

For example, the control unit 201 checks ROs stored in the memory unit208 when an access to the content is detected or a value of a specificconstraint contained in the RO becomes unavailable. In a case of anavailable RO is retrieved, the DRM content can be played.

Still referring to FIG. 2, the audio processing unit 204 converts audiodata into an analog signal and outputs the analog signal through aspeaker (SPK) in the form of an audible sound wave and converts theanalog signal input through a microphone (MIC) into audio data.

The input unit 205 can be implemented, for example, with at least one ofa keypad and a touch panel including a plurality of alphanumeric keysfor inputting text and numeric data and a plurality of function keys forexecuting various functions of the mobile terminal 200. The input unit205 receives a key input and outputs an input signal corresponding tothe key input to the control unit 201. The control unit 201 executes atask indicated by the input signal.

The RF unit 206 is responsible for radio communication with a cellularnetwork or any other type of wireless communication network. The RF unit206 includes an RF transmitter for up-converting and amplifying thesignal to be transmitted and an RF receiver for low-noise amplifying anddown-converting the received signal.

The data processing unit 207 includes a transmission portion forencoding and modulating a signal to be transmitted through the RF unit205 and a reception portion for demodulating and decoding the signalreceived through the RF unit 205.

The memory unit 208 includes a program memory region and a data memoryregion. The program memory region stores the operating system forbooting up the mobile terminal 200 and application programs. The datamemory region stores user data with the execution of the applications.The user data can be copied from an external storage such as portablememory and hard disc or downloaded from a remote server or other mobileterminal through a wired or wireless communication channel.Particularly, the user data include DRM contents.

The camera unit 209 converts an image projected on a lens into anoptical signal and converts the optical signal into a digital signal.The video processing unit 210 converts the digital signal output by thecamera unit 209 into a video signal for generating screen data.

The display unit 211 displays the screen data output by the videoprocessing unit 210. The display unit 211 is implemented with a flatpanel display, such as a liquid crystal display (LCD) having atouchscreen function. In this case, the display unit 211 can be a partof the input unit 206. When a content is used to the usage limit of aconstraint contained in the corresponding RO, the display unit 211 maydisplay a RO package acquisition solicitation message under the controlof the control unit 201.

Although the mobile terminal is described above with the structuredepicted in the exemplary drawings, it will be understood that at leastone of the internal units of the mobile terminal may be omitted, orreplaced by another functional unit. In addition at least anotherfunctional unit not shown in the drawings, may be added to the mobileterminal. In other words the functional units could be fewer or greaterthan those shown in the examples, and may have different functionality.

For example, the mobile terminal 200 may provided with a memory slot forreceiving external storage media such as memory card, a short rangecommunication module such as Infrared Data Association (IrDA) andBluetooth, multimedia module such as MP3 module, electronic transactionmodule such as mobile banking chip and traffic card chip, broadcastreceiver module, data communication port for exchanging data with otherdevices, battery module, and power charging module.

FIG. 3 a is a flowchart illustrating an example of a rights objectacquisition method according to an exemplary embodiment of the presentinvention.

In FIG. 3 a, a mobile terminal, such as, for example, the mobileterminal 200 shown in FIG. 2, operates in an idle mode (S301). Whileoperating in the idle mode, the mobile terminal 200 determines whether aDRM content execution mode has been activated (S303). The DRM contentexecution mode is activated when an access event (consumption, update,or purchase) to a specific DRM content object is detected.

If a DRM content execution mode is activated at step (S303), the mobileterminal generates a DRM content object list in response to a DRM ROacquisition command input by the terminal user 150 (S305).

The DRM content objects are encrypted multimedia files to whichcorresponding ROs are not acquired or nearly expired in association withtheir constraints.

In order to generate the DRM content object list (S305), the terminalgenerates a RO Acquisition Protocol (ROAP) trigger request (commonrights object acquisition request) message for requesting information onthe DRM content objects selected or approved by the terminal user 150.

The ROAP trigger request message includes a content identifier (CID,contentID) of at least one DRM content object. The ROAP trigger requestmessage may further include at least one of a device identifier (DeID)of the mobile terminal 200, permissions of individual ROs, andconstraints for restricting the permissions.

Permissions are actual usages or activities allowed over protectedcontent. For example, in the case of content granted only, the “display”permission can be only displayed, and the content granted the “display”and “print” permissions can be displayed and printed.

The mobile terminal 200 generates an ROAP trigger request messagecontaining the DRM content list and sends the ROAP trigger requestmessage to the RI. In this exemplary embodiment, the mobile terminal 200is connected through at least one wired or wireless communicationnetworks.

The RI generates a ROAP trigger (a common rights object acquisitionresponse) message with reference to the CIDs of the contents listed inthe ROAP trigger request message and transmits the ROAP trigger messageto the mobile terminal 200. At this time, costs for purchasing thecontents are contained in the ROAP trigger message. The ROAP triggermessage contains at least one of the RO identifier (roID) assigned tothe content. The ROAP trigger message may contain at least one rightsobject acquisition address of the content (roapURL) element, RIidentifier (RIID), RI Alias, Domain ID, Domain Alias, and Nonce. TheNonce element is a random value of 32 or 64 bits assigned by the RI.

The control unit 201 receives the ROAP trigger message and generates theDRM content list composed of contents. At this time, the control unit201 displays purchasing cost information on the screen of the displayunit 211 for obtaining user consent.

In this exemplary embodiment, the RI generates and sends a ROAP triggermessage referencing RO identifiers assigned to ROs correspondingindividual contents. The mobile terminal 200 requests to RI an ROAPtrigger message for multiple contents through the ROAP trigger requestmessage.

Still referring to FIG. 3 a, after generating the DRM contents list atstep S305, the control unit 201 generates an RO Request message foracquiring ROs corresponding to the contents listed in the DRM contentslist (S307).

The RO Request message contains roIDs assigned to the ROs correspondingto the contents. The roIDs can be extracted from the ROAP triggermessage received from the RI in response to the ROAP trigger requestmessage. The RO Request message also contains parameters such as DeID,RIID, Nonce, request time, RO Information (RO Info), certificate chain,signature, and extensions.

Table 2 shows an exemplary RO Request message format according to anexemplary embodiment of the present invention. In Table 2, the RORequest message contains roIDs (ro11, ro53, and ro97) of three contentsselected by the user and a nonce identical with that contained in theROAP trigger message. The roIDs also are contained the ROAP triggermessage received from the RI.

TABLE 2 <roap:roRequest xmlns:roap“urn:oma:bac:dldrm:roap-1.0”triggernonce=uPjd/olB1SkflpSrkhf/<roID>ro11; ro53; ro97</roID>

The mobile terminal 200 sends the RO Request message to the RI through awired or wireless communication network (S309).

Moreover, the RI may verify the RO Request message. In this case, if theRO Request message is successfully verified, the RI generates a ROResponse message and sends the RO Response to the mobile terminal 200.

The RO Response message states a plurality of protectedROs. With the<roap:protectedRO> element, a plurality of values can be contained in asingle RO Response message without increasing computation amount sincethe values of the rights objects decrease by using a hash algorithm.

After sending the RO Request message, the control unit 201 determineswhether a RO Response message has been received in response to the RORequest message (S311). The RO Response message contains ROscorresponding to the DRM content objects.

Table 3 shows an exemplary RO Response message according to an exemplaryembodiment of the present invention. In Table 3, the RO Response messagecontains the roIDs (ro11, ro53, and ro97) indicating the ROs issued bythe RI.

TABLE 3 <roap:roResponse xmlns:roap“urn:oma:bac:dldrm:roap-1.0”status=“Success”<nonce>uPjd/olB1SkflpSrkhf/ <roID>ro11; ro53; ro97</roID>

The RO Response message also contains parameters such as Status, DeID,RIID, ProtectedRO, Certificate Chain, Online Certificate Status Protocol(OCSP), OCSP Response, Signature, and Extensions.

A Nonce can be optionally contained in the RO Response message. In thiscase, the Nonce is identical with that of the ROAP trigger message andRO Request message. In other words, the RO Response message is the ROAPtrigger message and RO Request message contain the same Nonce.

FIG. 3 b is diagram illustrating a data structure of an RO responsemessage according to an exemplary embodiment of the present invention.

The RO response message is sent from the RI to the mobile terminal inresponse to an RO Request message. As shown in FIG. 3 b, the RO Responsemessage includes the protected ROs (protectedRO) for individualcontents, and each protectedRO contains at least one permission with atleast one constraint. In a case of RO Response message for a multipartDCF containing an MP3 file and an image file, two protectedRO arecarried by the RO Response message. The protectedRO may contain a “play”permission with a constraint element set to “one month” or “one week and7 times”. For example, the value of “one week and 7 times” of theconstraint element means that the MP3 file is restricted to be played 7times during a week. The protectedRO may contain a “display” permissionwith “one month”, “ten times” or “one month and ten times”. That is, theconstraints are dependent on the permissions.

Moreover, the permissions include “play”, “display”, “execute”, and“print”. The constraints include “count”, “timed-count”, “datetime”,“interval”, “individual”, and “system”.

If an RO Response message is received from the RI 250, the control unit201 of the mobile terminal 200 acquires the ROs corresponding to thecontents from the RO Response message (S313).

The control unit 201 updates the contents with the acquired ROs. Theupdate means to extend the usage rights on the expired contents orenable consumption of the newly downloaded contents.

FIG. 4 is a message flow diagram illustrating a rights objectacquisition method according to an exemplary embodiment of the presentinvention.

Referring to FIG. 4, the rights object acquisition method of FIG. 3 a isdescribed primarily with message flows between the mobile terminal 200and RI 250 connected through wired/wireless communication network andinteractions between a terminal user 150 and the mobile terminal 200.

The control unit 201 of the mobile terminal 200 enters into a DRMcontent execution mode in response to a predetermined event (S401). Ifthe mobile terminal 200 enters into the DRM content execution mode, thecontrol unit 201 controls the display unit 211 displays a DRM contentlist or a RO package acquisition solicitation message on a screen(S403). FIG. 11 a is a screen image illustrating a step of displayingthe DRM content list in FIG. 4, and FIG. 11 b is a diagram illustratingan exemplary information field structure of a DRM content list of FIG.11 a.

As shown in the example in FIG. 11 a, the DRM content list is generatedwith the DRM content objects of which usage rights have expired or areclose to expiration. The control unit 201 retrieves the DRM contentobjects from DRM content database stored in the memory unit 208.

Now referring to FIG. 4 again, while displaying the DRM content list,the terminal user 150 selects at least one DRM content object for whichan RO is acquired and sets constraints associated with usage durationand times of the content (S405).

If the content selection and constraint settings are completed, thecontrol unit 201 generates an ROAP trigger request with the settings ofthe selected contents and sends RO Request to the RI 250 (S407).

In response to the generating and sending of the ROAP trigger request,if a ROAP trigger request is received, the RI 250 generates an ROAPtrigger with reference to the settings contained in the ROAP triggerrequest and sends the ROAP trigger to the mobile terminal 200 (S409).The ROAP trigger may contain, for example, information on the prices ofthe ROs. In this case, the mobile terminal 200 calculates a purchasingcost on the basis of the prices and displays the information thepurchasing cost on the screen (S411). Also, the mobile terminal 200outputs a message asking whether to confirm or cancel the purchase onthe RO.

Still referring to FIG. 4, the terminal user 150 decides whether toconfirm or cancel the purchase on the RO (S413). If the terminal user150 cancels the purchase, the mobile terminal 200 repeats step S403 suchthat the user selects the DRM content objects and sets the constraintagain at step S405.

If the terminal user 150 confirms the purchase on the RO, the mobileterminal 200 generates a RO Request (roRequest) message for acquiringthe purchase-confirmed RO and sends the roRequest message to the RI 250(S415).

If a purchase-confirm command is input through the input unit 205, themobile terminal 200 processes a payment for purchasing the RO with theRI 250 through an authentication or mobile banking procedure. For thisreason, the mobile terminal 200 is provided with, for example, anelectronic transaction module or a mobile banking module.

If the roRequest message is received, the RI 250 generates an ROresponse (roResponse) message containing the requested DRM RO and sendsthe roResponse message to the mobile terminal 200 (S417).

If the roResponse message is received, the mobile terminal 200 acquiresthe purchased DRM RO from the roResponse message (S419).

In a case of an RO acquisition for free content or post-payment content,the price exchange, purchase confirmation, and payment steps can beskipped.

FIG. 5 is a flowchart illustrating an example of a DRM content objectlist generation procedure of the rights object acquisition method ofFIG. 3 a, and FIG. 6 is a message flow diagram illustrating exemplarymessage flows between entities in the DRM content list generationprocedure of FIG. 5. In FIGS. 5 and 6, it is assumed that the DRMcontent list is composed of items representing DRM content objectsstored within the memory unit 208 of the mobile terminal 200, at stepS305 of FIG. 3 a.

A DRM RO acquisition system for implementing the RO acquisition methodaccording to the present invention includes a mobile terminal 200 forrequesting the ROs for composite contents and an RI 250 for issuing theROs to the mobile terminal 200 (see FIGS. 6, 8 and 10). The RI 250 sendsadditional information on a number of available constraint updates andprice information of the respective ROs to the mobile terminal 200.

The mobile terminal 200 operates in the DRM content execution mode (S501and S601). In the DRM content execution mode, the mobile terminal 200then determines whether at least one reference constraint value of a DRMcontent object has been set (S503). The reference constraint values areset, for example, to judge maturity of the expiration of the usage timesand duration of the DRM content object. For example, the referenceconstraint value can have the remaining available usage times set to 1,or have the remaining available usage duration set to 1 hour. In a casethat the reference constraint values have not been set, the mobileterminal 200 may output a reference constraint value setup solicitationmessage (S505). Accordingly, the mobile terminal 200 sets a referenceconstraint value according to a user manipulation of a series of setupmenu screens (S507).

Next, the mobile terminal determines whether there is at least one DRMcontent object of which usage right has expired, or is close toexpiration/exhaustion, with reference to the reference constraint value(S509). In other words, the mobile terminal 200 retrieves the DRMcontent objects of which usage right has expired, or is about to expire(e.g. nearly expired), from the memory unit 208 of the mobile terminal200. If no DRM content object of which the usage right has expired or isclosed to expiration, the mobile terminal executes a command input bythe terminal user 150 in association with a DRM content object (S517).

If at least one DRM content object of which RO has a constraint valueequal to or less than the reference constraint value (update candidateobject) exists, the mobile terminal 200 generates and displays an updatecandidate object list composed of the update candidate objects togetherwith file information of the individual update candidate DRM contentobjects (S511 and S603). The file information includes remained usagetimes and durations of the individual DRM content objects.

Next, the mobile terminal 200 detects a user command and determineswhether a user command is an object selection command for selecting aspecific DRM content object from the update candidate object list (S513and S605).

The ROs associated with DRM content objects selected on the updatecandidate DRM content list are acquired (purchased). The DRM contentobject selected by the user is presented with a marker marked in a checkbox provided at a side of the DRM content object as shown in FIG. 11 a.

The DRM content list structured in the form of a table as shown in theexample in FIG. 11 b. The DRM content table is composed of, for example,a serial number field, a content name field, a remaining usage rightfield, and another field. An example of usage of the other field is fora file extension indicating the type of the content. The DRM contentlist may provide information obtained from the RI 250. For example, aninformation field can be provided for indicating information receivedfrom the RI 250 such as updated times of available constraintsassociated with the DRM contents and prices of the right objects. TheDRM content list can be displayed with the RO package acquisitionsolicitation message for obtaining user consent.

If the user command is not an object selection command, the mobileterminal 200 determines whether the user command is an objectconsumption command for consuming at least one update candidate objectof which associated constraint has not expired (S515). If the usercommand is an object consumption command for consuming a specific updatecandidate object of which associated constraint has not expired, themobile terminal 200 consumes the specific update candidate object(S517).

However, if the user command is not an object consumption command orthere is no update candidate object of which associated constraint hasnot expired, the mobile terminal ends the DRM object consumption mode.

In the meantime, if the user command is an object selection command (atstep S513), the mobile terminal 200 generates an ROAP trigger requestwith an object package containing at least one update candidate objectselected by the user command (S519 and S607).

The ROAP trigger request includes but is not limited to CIDs of selectedDRM contents. As described above, the ROAP trigger request may includeat least one of the DeID of the mobile terminal 200, permissions or ROsto the contents, and constraints restricting permissions.

The constraints (i.e., the restriction information of the ROscorresponding to the DRM contents) can be selected by DRM content or setwith same usage times or duration. If the user sets the constraints forthe DRM contents through a webpage of the RI 250, the mobile terminal200 accesses the RI 250 through the wired/wireless network, so as to setthe constraints for the DRM contents stored in the mobile terminal 200.

After generating the ROAP trigger request in the above manner, themobile terminal 200 sends the ROAP trigger request to the RI 250 throughthe wired/wireless communication network (S521).

If the ROAP trigger request is received, the RI 250 generates a ROAPtrigger and sends the ROAP trigger to the mobile terminal 200 inresponse to the ROAP trigger request (S609). The ROAP trigger is senttogether with the price information on the corresponding DRM contents.

The ROAP trigger contains roIDs assigned the ROs corresponding to theDRM contents. Also, the ROAP trigger may contain ROAP address (roapURL)or the RI 250. The ROAP trigger may further selectively contain one ormore of the RI ID, RI Alias, Domain ID, and Domain Alias.

When security is required, the RI 250 sends the ROAP trigger having aNonce value to the mobile terminal 200.

After transmitting the ROAP trigger request, the mobile terminal 200determines whether a ROAP trigger and price information is received(S523).

If a ROAP trigger and price information is received, the mobile terminal200 displays the price information on the screen of the display unit 211(S525 and S611). For example, a guide message “total price is 2500 won.Do you want to purchase the DRM contents package?” is displayed fornotifying the user of the total price of the DRM ROs.

Next, the mobile terminal 200 detects a user command and determineswhether the user command is a purchase approval command (S527). If theuser command is not a purchase approval command, the control unit 201determines that the user command is a purchase cancellation command andrepeats step S513 such that the terminal user 150 reselects DRMcontents. If the user command is a purchase approval command, thecontrol unit 201 generates a purchase-approved DRM content list of whichROs are to be purchased in an in package (S529 and S615). It should beunderstood that a purchase should be defined broadly and could, forexample, include a prepaid account where a purchase is a deduction froma prepaid balance

After generating the DRM contents list, the mobile terminal 200generates an RORequest message with the DRM contents list at step S307of FIG. 3 a.

FIG. 7 is a flowchart illustrating an example of a DRM content listgeneration procedure of the rights object acquisition method of FIG. 3 aaccording to another exemplary embodiment of the present invention, andFIG. 8 is a message flow diagram illustrating exemplary message flowsbetween entities in the DRM content list generation procedure of FIG. 7.

In FIGS. 7 and 8, it is assumed that the mobile terminal 200 hasreceived the price information of the DRM contents from the RI 250.

The mobile terminal 200 operates in the DRM content execution mode (S701and S801). In the DRM content execution mode, the control unit 201 ofthe mobile terminal 200 determines whether at least one DRM contentobject exists in the memory unit 208 (S703). If no DRM content objectexists in the memory unit 208, the mobile terminal 200 maintains astandby state. If at least one DRM content object exists, the mobileterminal 200 connects to the RI 250 through a wired/wirelesscommunication network and sends a stored DRM content list listing theDRM content objects stored within the memory unit 208 (S705 and S803).Next, the mobile terminal 200 receives price information on the ROsassociated with the DRM content objects listed in the DRM content listfrom the RI 250 (S707 and S805).

Still referring to FIGS. 7 and 8, after receiving the price information,the mobile terminal 200 determines whether a reference constraint valueof ROs corresponding to the DRM content objects (S709) is set.

If no reference constraint values of ROs are set, the mobile terminal200 displays a reference constraint value configuration solicitationmessage (S711) and configures a reference constraint value in accordancewith user input (S713). If the reference constraint value is configured,the mobile terminal 200 determines whether at least one DRM contentobject of which RO has a constraint value equal to or less than thereference constraint value exist in the memory unit 208 (S715).

If no DRM content object of which RO has a constraint value equal to orless than the reference constraint value exists, then the mobileterminal 200 consumes a DRM content object selected by the user (S723).

On the other hand, if at least one DRM content object of which RO has aconstraint value equal to or less than the reference constraint value(update candidate object) exists, the mobile terminal 200 generates anddisplays an update candidate object list composed of the updatecandidate objects together with contents information of the individualupdate candidate objects (S717 and S807). The file information alsoincludes residual usage times and duration of the individual DRM contentobjects.

Next, the mobile terminal 200 detects a user command and determineswhether a user command is an object selection command for selecting aspecific DRM content object from the update candidate object list (S719and S809). If the user command is not an object selection command, themobile terminal 200 determines whether the user command is an objectconsumption command for consuming at least one update candidate objectof which an associated constraint has not expired (S721). If the usercommand is an object consumption command for consuming a specific updatecandidate object of which associated constraint has not expired, themobile terminal 200 consumes the specific update candidate object(S723).

If the user command is not an object consumption command or there is noupdate candidate object of which associated constraint has not expired,the mobile terminal ends the DRM object consumption mode.

In the meantime, if the user command is an object selection command atstep S719, the mobile terminal 200 generates a temporary DRM contentslist composed at least one update candidate object selected by the usercommand (S725 and S811).

Next, the mobile terminal 200 calculates a cost for purchasing theobjects listed in the temporary DRM contents list on the basis of priceinformation received, at step S707, from the RI 250 (S727 and S813) anddisplays the purchase cost (S729 and S815).

While displaying the purchase cost, the mobile terminal 200 detects auser command input by the terminal user 150 and determines whether theuser command is a purchase approval command (S731 and S817). If the usercommand is not a purchase approval command, the mobile terminal 200regards the user command is a purchase cancellation command, so as torepeat steps S715 to S731.

If the user command is a purchase approval command, the mobile terminal200 generates a DRM contents list of which ROs to be purchased in apackage (S733 and S819).

After generating the DRM contents list, the mobile terminal 200 thengenerates an RO Request message with the DRM contents list at step S307of FIG. 3 a.

FIG. 9 is a message flow diagram illustrating an example of a rightsobject acquisition method according to another exemplary embodiment ofthe present invention.

Referring to FIG. 9, if an RO acquisition command is input for acquiringROs corresponding to one or more DRM content objects, the mobileterminal 200 generates an ROAP Trigger Request message and sends theROAP Trigger Request message to the RI 250 (S910). The ROAP TriggerRequest message includes at least one content identifier (CID). The ROAPTrigger Request message also includes at least one of the deviceidentifier (DeID) of the mobile terminal 200 and constraints forrestricting the usage rights of the selected content objects.

In a case that a parent license of at least two child licenses exists,the ROAP Trigger Request message may further includes the parent licenseinformation. For example, in order to acquire two ROs for a track 1 anda track 3 dependent on a music album A, the ROAP Trigger Request messagemay include an identifier of album A in addition to the identifiers ofthe track 1 and track 2. In this case, the ROs for the track 1 and track3 can be acquired only with the RO for the album A afterward.

By constraining the play permissions of the track 1 and track 3 with aparent RO, either track 1 and track 3 can be played up to a total usagetimes restricted by a constraint of the parent RO.

Also, different parent licenses can be applied. For example, the usermay create a content list (e.g., my list and favorite list) as a parentgroup. In this case, the rights objects of the content objects listed inthe content list depends on the multiple rights object for the contentlist.

The DRM content object may comprise a content object that is receivedfrom another device (for example, another terminal or server) but hasnot acquired a corresponding RO, or of which the RO has expired.

The mobile terminal 200 selects an RI for purchasing an RO of at leastone DRM content object with reference to an RI's Uniform ResourceLocation (URL) information contained in the header information of theDRM content object. The ROAP Trigger Request message is sent to the RIURL.

In order to send the ROAP Trigger Request message, a DCF structure hasan additional field indicating the address of the RI 250 for acquiringmultiple ROs in a composite manner.

FIG. 13 is a diagram illustrating a structure of DCF proposed for therights object acquisition method according to an exemplary embodiment ofthe present invention.

In FIG. 13, a BatchRIURL 1310 is an address of RI which is issuing amultiple RO, and a BatchRIURLLength 1320 indicates a length of theBatchRIURL 1310.

The BatchRIURLLength 1320 is optional information, so as not to beincluded in the DCF structure.

At least one BatchRIURL is included in a DCF structure. The greater anumber of BatchRIURL is, the more the ROs content objects can be sent.

For example, if a content A includes a BatchRIURL A and a content Bincludes a BatchRIURL B, it can be difficult to acquire the ROs of thecontents A and B in a composite manner. However, if the BatchRIURLs Aand B are included in the content A, the ROs of the contents A and B canbe acquired in a composite manner since the common RI address B fromwhich the ROs of the two contents A and B can be acquired exist.

In a case that at least two BatchRIURLs exist from which ROs of thecontent objects can be acquired, a BatchRIURL having a best quality andreliability (for example, an address of the RI servicing at higher datarate or a superior capability) can be selected. For this purpose, themobile terminal 200 manages the BatchRIURLs or equivalent information ofthe content objects in the form of a list or a database.

The BatchRIURL field can be added within the common header of the DCFstructure as a mandatory field or included in an extended header field,which is mandatory field, located in the common header.

Also, the mobile terminal 200 may select an RI for acquiring ROs of theDRM content objects in a composite manner with reference to the RI URLsstored in the memory unit 208 and send an ROAP Trigger Request messageincluding the selected RI URL. Also, the mobile terminal 200 may requestan RI URL for receiving ROs of the DRM content objects to the RI 250 andsend an ROAP Trigger Request message to the RI URL received from the RI250. The RI URL received from the RI 250 is typically stored within thememory unit 208 and uses for acquiring the ROs in a composite mannerlater.

In response to the ROAP Trigger Request message, the RI 250 generates aROAP Trigger message and sends the ROAP Trigger message to the mobileterminal 200 (S920). The ROAP Trigger message may include priceinformation on the ROs of the content objects indicated by the ROAPTrigger Request message. Also, the ROAP Trigger message may include oneor more roIDs to identify the ROs corresponding to the content objects.The ROAP trigger message may include at least one of roapURL, RI ID, RIAlias, Domain ID, Domain Alias, and Nonce.

The ROAP Trigger request message and ROAP Trigger message can be sent inthe form a HTTP GET or a HTTP POST (see RO acquisition mechanism of OMADRM v2.0). In a multiple RO acquisition method for acquiring multipleROs simultaneously, the message length may increase, whereby HTTP POSTprefers to send the ROAP messages.

In addition, the mobile terminal 200 may display the price informationon the screen for user reference.

If the RO Trigger message is received, the mobile terminal 200 generatesan RO Request message for requesting one or more ROs corresponding tothe DRM content objects and sends the RO Request message to the RI 250(S930). The ROs may be identical with those indicated in the RO TriggerRequest message or may not be identical with those indicated in the ROtrigger Request message. That is, the DRM content objects for which ROsare to be acquired may be changed by the user.

If the RO Request message is received, the RI 250 generates an ROResponse message containing the ROs indicated in the RO Request messageand sends the RO Response to the mobile terminal (S940).

Consequently, the mobile terminal 200 can acquire the ROs by extractingthe ROs contained in the RO Response message in a batch processingmanner.

The procedure (S910 to S940) can be applied in an abnormal situation.For example, if the DCF of FIG. 13 includes an abnormal header such as aSilent header, or a Preview header for carrying free contents withoutuser interaction for payment and purchase approval, the RO acquisitionprocedure S910 to S940 may be progressed as a background operation underthe negotiation between the mobile terminal 200 and RI 250. In thiscase, address information for acquiring a multiple of ROs such as asilent group URL (silent-group-url) may included in the abnormal headersuch that the mobile terminal 200 can access to the RI with reference tothe silent group URL to acquire the DCF files, i.e. the ROs of the DRMcontent objects.

For the background execution of the RO acquisition procedure,permissions, constraints, and purchase information are selectivelyincluded in the DCF structure in addition to the silent header. Thepermissions may include at least one of “play”, “display”, “execute”,“print”, and “export” permissions. The constraints may include at leastone of “count”, timed-count”, “datetime”, “interval”, “individual”, and“system”. The constraints are dependent on the individual permissions.The purchase information may include prices of the content objects andcontract policies such as a fixed charge system and a metering-basedcharge system.

The silent group URL, permissions, constraints, and purchase informationcan be included in additional parts for allowing the user to theparameters therein, or in mandatory parts for protecting the parametersfrom being tampered. The RO Response message may further include aSession ID for establishing a session between the mobile terminal 200and the RI 250.

FIG. 10 is a message flow diagram illustrating a right objectacquisition method according to another exemplary embodiment of thepresent invention.

Referring to FIG. 10, if an RO acquisition command is input foracquiring ROs corresponding to one or more DRM content object, themobile terminal 200 generates an ROAP Trigger Request message and sendsthe ROAP Trigger Request message to the RI 250 (S1010).

The ROAP Trigger Request message includes one or more DRM contentidentifiers (CIDs). Also, the ROAP Trigger Request message also includesat least one of the device identifier (DeID) of the mobile terminal 200and constraints for restricting the usage rights of the selected contentobjects. The DRM content objects are either the content objects receivedfrom another mobile terminal or downloaded from a server or the contentobjects of which right objects has expired or are close to expires.

Here, the mobile terminal 200 selects an RI for purchasing the ROscorresponding to the DRM content objects with reference to the RI URLinformation and sends the ROAP Trigger Request message to the selectedRI.

If the ROAP Trigger Request message is received, the RI 250 generates anROAP Trigger message and sends the ROAP Trigger message to the mobileterminal 200. The ROAP Trigger message includes the price information onthe ROs corresponding to the content objects indicated by the ROAPTrigger Request message. The ROAP Trigger message further includes roIDsassigned to the individual ROs. The ROAP Trigger message furtherincludes at least one of RI ID, RI Alias, Domain ID, Domain Alias, andNonce.

If the RO Trigger message is received, the mobile terminal 200 generatesan RO Request message for requesting one or more ROs corresponding tothe DRM content objects and sends the RO Request message to the RI 250(S1030).

In response to the RO Request message, the RI 250 generates an ROResponse message containing the ROs indicated in the RO Request messageand sends the RO Response to the mobile terminal (S1040). The ROResponse message may include a session ID.

If the RO Response message is received, the mobile terminal 200 extractsthe ROs from the RO Response message. In a case that a session ID isincluded in the RO response message, the mobile terminal 200 establishesa session with the RI 250 on the basis of the session ID and sends a ROConfirm Request message to the RI 250 through the session (S1050). Sincethe RO Confirm Request message includes a parameter such as “RO ConfirmInfo”, the RI 250 is acknowledged the successful RO acquisition.

Upon receiving the RO Confirm Request message, the RI 250 checks thatthe requested ROs are successfully issued and determines whether to endthe session or resend the RO Response message. If the parameter “ROConfirm Info” is included in the RO Confirm Request message, the RI 250determines that the ROs are successfully issued and thus send an ROConfirm Response message to the mobile terminal 200.

The RO acquisition method of the present invention can be implementedwithout BatchRIURL in the DCF structure.

FIG. 12 is a message flow diagram illustrating a rights objectacquisition method according to another exemplary embodiment of thepresent invention. In this embodiment, the DRM content object iscontained with individual RI URLs rather than BatchRIURL in the DCF.

Referring to FIG. 12, if a multiple RO acquisition command is input bythe terminal user, the mobile terminal 200 generates a ROAP TriggerRequest message containing CIDs of individual DRM content objects andsends the ROAP Trigger Request message to the RI 250. Here, the mobileterminal 200 sends the ROAP Trigger Request message to the RI 205 withreference to an RI URL of one of multiple DRM content objects.

If the RI 250 received the ROAP Trigger Request message has no multipleRO transmission capability, the RI 250 sends a Redirection messagenotifying a new URL of another RI, which has the multiple ROtransmission capability, to the mobile terminal 200 (S1220). Theredirection message can be one, for example, of HTTP 302, HTTP 303, andHTTP 307 messages proposed in OMA DRM.

If the Redirection message is received, the mobile terminal 200 sendsthe ROAP Trigger Request message to the RI 300 indicated by the RI URLcontained in the Redirection message (S1230). Accordingly, the mobileterminal 200 acquires the ROs from the RI 300 through the procedure ofFIG. 9 or FIG. 10.

As described above, the ROAP Trigger Request message and ROAP Triggermessage can be exchanged in the form of HTTP GET or HTTP POST message.Also, the ROAP Trigger Request message and ROAP Trigger message can beexchanged in the format, i.e., HTTP GET or HTTP POST, designated by theRI.

FIG. 14 is a message flow diagram illustrating a rights objectacquisition method according to another exemplary embodiment of thepresent invention.

Referring to FIG. 14, the if a multiple RO acquisition command is inputby the user, the mobile terminal 200 generates a ROAP Trigger Requestmessage containing a CIDs of individual DRM content objects and sendsthe ROAP Trigger Request message to the RI 250.

After transmitting the ROAP Trigger Request message, the mobile terminal200 and RI 250 initiate a web transaction. At this time, the user canconfigure the permissions of ROs corresponding to the content objectstogether with constraints. For example, if the RI 250 publishes pricesof the ROs associated with the content objects, the mobile terminal 200generates acquisition request information on the ROs approved by theuser and sends the acquisition request information to the RI 250.

After the web transaction has completed by user's approval, the RI 250generates an ROAP Trigger message associated with the ROs to be acquiredand sends the ROAP Trigger message to the mobile terminal 200 (S1430).

If the ROAP Trigger message is received, the mobile terminal 200generates an RO Request message for acquiring the ROs and sends the RORequest message to the RI 250 (S1440).

Upon receiving the RO Request message, the RI 250 then issues the ROsindicated by the RO Request message and sends a RO Response messagecontaining the ROs to the mobile terminal 200.

Consequently, the mobile terminal 200 acquires the ROs from the ROResponse message in a composite manner.

Although the web transaction is performed after the ROAP Trigger Requestmessage is transmitted to the RI 250, it is obvious to those of ordinaryskill in the art that the web transaction can be performed at any timingand multiple times. For example, the web transaction can be performedprior to the transmission of the ROAP Trigger Request message. In thiscase, the user may complete all the manipulations required for paymentduring the web transaction. Also, the web transaction can be initiatedone or more times before and after the transmission of the ROAP TriggerRequest message for changing the payment conditions.

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

As described above, the rights object acquisition method and apparatusof the present invention enables acquiring multiple rights objects in acomposite manner, thereby improving user convenience. Also, the rightsobject acquisition method of the present invention can be associatedwith discount policy for bundle purchase of the content providers,thereby promoting sales in view of the content provider and reducingpurchase cost in view of the consumer. Also, the rights objectacquisition method of the present invention provides an improved DCFstructure enabling acquisition of multiple rights objects in a compositemanner, resulting in improvement of DRM technology.

What is claimed is:
 1. A rights object acquisition method comprising:transmitting a Rights Object Acquisition Protocol (ROAP) trigger requestmessage initiating a session of downloading a multiple Rights Objects(ROs) corresponding to multiple contents to a Rights Issuer (RI)indicated in headers of the multiple contents; receiving an ROAP triggermessage from the RI in response to the ROAP trigger request message;transmitting to the RI an RO request message to request for ROscorresponding to one or more contents selected among the multiplecontents in response to the ROAP trigger message; and receiving a ROresponse message including the ROs corresponding to one or more contentsfrom the RI.
 2. The method of claim 1, wherein the multiple contents arestructured in a Digital Rights Management (DRM) Content Format (DCF) andhave the headers of the multiple contents comprises a DCF header.
 3. Themethod of claim 2, wherein the DCF header comprises a common headerindicating an address of the RI for use in acquiring the multiple ROs ina batch.
 4. The method of claim 3, wherein the common header comprises aBatchRIURL indicating the address of the RI.
 5. The method of claim 3,wherein the common header comprises a BatchRIURLLength optionally. 6.The method of claim 1, wherein the ROAP trigger request message and theROAP trigger message are transmitted in one of Hyper Text TransferProtocol (HTTP) GET method and HTTP POST method.
 7. The method of claim1, wherein the ROAP trigger request message is transmitted to one of theaddress of RI commonly indicated in the headers of the multiple contentsand the address of the RI stored previously in a device.
 8. The methodof claim 1, wherein the ROAP trigger request message comprises multipleContent Identifiers (CIDs) allocated to the multiple contentsrespectively.
 9. The method of claim 8, wherein the ROAP trigger messagecomprises multiple RO Identifiers (roIDs) of the multiple ROscorresponding to the multiple CIDs.
 10. The method of claim 10, whereinthe RO request message comprises one or more roIDs corresponding to oneor more contents selected among the multiple roIDs included in the ROAPtrigger message.
 11. The method of claim 10, wherein the RO responsemessage comprises one or more ROs corresponding to the one or more roIDsincluded in the RO request message.
 12. The method of claim 2, whereinthe DCF comprises information for use in requesting the ROsautomatically.
 13. The method of claim 12, wherein the DCF comprises atleast one of a Silent and Preview headers for acquiring the ROs onbackground silently without user interaction.
 14. The method of claim 9,wherein the Silent header and Preview header comprises an address of theRI for acquiring the multiple ROs corresponding to the multiple contentsin a batch.
 15. The method of claim 1, further comprising: transmittingthe ROAP trigger request message to the RI corresponding to the RIaddress indicated in at least one of the plural contents; receiving anew RI address for redirection from the RI; and retransmitting the ROAPtrigger request to a new RI corresponding to the new RI address.
 16. Themethod of claim 1, further comprising including, when constraintsrestricting a right range of the RO of the content is divided into ahigh layer and a low layer and at least two ROs on the high and lowlayers are required for a specific content, information requesting forRO acquisition of the high layer for the specific content in the ROAPtrigger request message.
 17. A Rights Object (RO) acquisition methodcomprising: storing multiple contents structured in a Digital RightsManagement (DRM) Content Format (DCF); transmitting a request message ofrequesting for multiple ROs to a Right Issuer (RI) represented by RIaddress indicated in a common header of multiple contents in response toan acquisition request for multiple ROs corresponding to the multiplecontents; receiving a response message including the multiple ROs fromthe RI in response to the request message; and acquiring the multipleROs corresponding to the multiple contents from the response message.18. The method of claim 17, wherein the common header comprises aBatchRIURL indicating an address of the RI for acquiring the ROscorresponding to the multiple contents and is positioned in DCF headerof the multiple contents.
 19. The method of claim 17, furthercomprising: transmitting to the RI a Right Object Acquisition Protocol(ROAP) trigger request message including multiple Content Identifiers(CIDs) allocated to the multiple contents; receiving an ROAP triggermessage including multiple RO Identifiers (roIDs) allocated to themultiple ROs corresponding to the multiple CIDs; transmitting to the RIan RO request message including at least one roID corresponding to atleast one content selected among the multiple contents after receivingthe ROAP trigger message; receiving an RO response message including atleast one RO corresponding to the at least one roID from the RI; andacquiring at least one RO for the at least one content from the ROresponse message.
 20. The method of claim 19, wherein the ROAP triggerrequest message and the ROAP trigger message are transmitted in one ofHyper Text Transfer Protocol (HTTP) GET method and HTTP POST method. 21.The method of claim 17, wherein the transmitting a request message to aRI comprises: checking the common header of at least one of the multiplecontents; and selecting the RI by referencing the RI address providingthe multiple ROs corresponding to the multiple contents from the commonheader.
 22. A device comprising: a memory which stores contentsstructured in a Digital Rights Management (DRM) Content Format (DCF),Rights Objects (ROs) corresponding to the contents, and an address of anRights Issuer (RI); a communication unit which communicate messages foracquiring multiple ROs corresponding to multiple contents with the RI;and a control unit which controls transmitting a request message ofrequesting for multiple ROs to a Right Issuer (RI) represented by RIaddress indicated in a common header of multiple contents in response toan acquisition request for multiple ROs corresponding to the multiplecontents and acquiring the multiple ROs corresponding to the multiplecontents from the response message including the multiple ROs receivedfrom the RI in response to the request message.
 23. The device of claim22, wherein the common header comprises a BatchRIURL indicating anaddress of the RI for acquiring the ROs corresponding to the multiplecontents and is positioned in DCF header of the multiple contents. 24.The device of claim 22, wherein the request message and the responsemessage are transmitted in one of Hyper Text Transfer Protocol (HTTP)GET method and HTTP POST method.
 25. The device of claim 22, wherein theDCF comprises at least one of a Silent header and a Preview header. 26.The device of claim 25, wherein the control unit requests the RIspecified by one of the Silent header and Preview header for themultiple ROs automatically in one of the HTTP GET and HTTP POST methods.27. The device of claim 26, wherein the control unit processes themultiple ROs automatic request on background without user interaction.28. A Rights Object-providing system, the system comprising: a devicewhich requests a Rights Issuer (RI) specified in a common header ofmultiple contents for multiple Rights Objects (ROs) in response to anacquisition request for the multiple ROs corresponding to the multiplecontents; and the RI which provides the device with the multiple ROs inresponse to the multiple ROs request from the device.
 29. The system ofclaim 28, wherein the multiple contents are structured in a DigitalRights Management (DRM) Content Format (DCF).
 30. The system of claim28, wherein the common header is positioned in a DCF header andcomprises a BatchRIURL indicating the address of the RI for use inacquiring the multiple ROs in a batch.
 31. The system of claim 28,wherein the device transmits a Rights Object Acquisition Protocol (ROAP)trigger request message including multiple Contents Identifiers (CIDs)allocated to the multiple contents, transmits, when an ROAP triggermessage is received from the RI in response to the ROAP trigger requestmessage, to the RI an RO request message including multiple ROIdentifiers (roIDs) corresponding to the multiple contents, andacquiring, when an RO response message is received from the RI inresponse to the RO request message, the multiple ROs from the ROresponse message.
 32. The system of claim 31, wherein the RI transmitsto the device the ROAP trigger message including the multiple roIDsallocated to the multiple ROs corresponding to the multiple CIDs inresponse to the ROAP trigger request message and transmits, when the ROrequest message from the device in response to the ROAP trigger message,to the device the RO response message including the multiple ROscorresponding to the multiple roIDs.
 33. The system of claim 28, whereinthe DCF comprises at least one of a Silent header and a Preview header.34. The system of claim 33, wherein the device requests the RI specifiedby one of the Silent header and Preview header for the multiple ROsautomatically in one of the HTTP GET and HTTP POST methods.
 35. Thesystem of claim 34, wherein the device processes the multiple ROsautomatic request on background without user interaction.